Optical waveguide devices formed on planar substrates have become important elements for various optical network applications, including multiplexer and demultiplexer in dense wavelength division multiplexing (DWDM) systems and components in passive optical networks (PON). This technology allows multiple functional units to be integrated on a single substrate.
The key to forming optical waveguide devices on a planar substrate is the deposition process. In order to produce high quality devices, the deposition process must produce stable films that demonstrate low optical loss. Ideally, the deposition method should provide for high throughput as well as high quality devices.
Various methods have been used to form optical waveguide devices on a planar substrate. For example, halide materials have been used to form device layers. However, this method requires special handling of the corrosive halide materials. Another method that has been used is deposition at sub-atmospheric pressure; for example, sub-atmospheric plasma-enhanced chemical vapor deposition (PECVD). However, this method provides a lower deposition rate than the current invention. A third method that has been used is atmospheric pressure chemical vapor deposition (APCVD) using a showerhead configuration. However, this method provides less than optimal wafer-to-wafer uniformity than does the current invention.